Biomonitoring: Analysis of Toxic Metals in Chinese Privet by ICP-OES
Introduction
Pollution and its effects on the environment have been studied increasingly over the past decades as public awareness and government mandates demand solutions to the problems created by human industries.[1] The release of pollution into the environment is a persistent problem in Hamilton County. As the 4th largest industrial center in the state,[2] county pollution sources include manufacturing, fertilization, electricity generation, waste water treatment and mining operations.[3] Biomonitoring is one way to qualitatively and quantitatively investigate the changes in the environment due to pollution by anthropogenic sources. Indicators, such as mud-dwelling macroinvertebrates, fish, algae, and some aquatic plants, are involved in the biomonitoring process.[4] We will use the Chinese privet (Ligustrum sinense) to biomonitor for the presence of toxic metals.
Chinese privet is a plant
species that aggressively colonizes and prefers a damp habitat, such as low
woods, bottomlands, streamsides and disturbed areas. [5] This plant grows invasively throughout the
Tennessee River Valley and would be a useful tool for biomonitoring. In
collaboration with Dr. Henry Spratt (Department of Biological and Environmental
Sciences), we will collect Chinese privet for toxic metals analysis from
control plots along the Tennessee River Gorge.
Research Proposal
The goal of this proposal is to analyze the plant species Chinese privet for toxic metals using inductively coupled plasma – optical emission spectroscopy (ICP-OES). When using ICP-OES, the solid sample must first be dissolved before being submitted into the plasma.[6] Once in the plasma, the excited atoms emit light with specific wavelengths for each element; the emitted light is then calibrated against standards to provide a quantitative analysis for the original sample.[7] In addition to optimum excitation conditions, the inductive-coupled plasma offers high stability, low noise, low background and freedom from interferences.[8] Leaves and stems from the Chinese privet will be collected from the control plots and digested using a microwave bomb apparatus. Studies will be performed to determine the optimum digestion mixture and microwave power cycle to avoid sample losses. Calibration curves will be constructed from standard solutions (available from the National Institute of Standards and Technology, NIST) to directly analyze the environmental control samples. Once collection technique, sample digestion and analysis are optimized, Chinese privet from industrial contamination sites will be collected and analyzed.
Different factors should be recognized when biomonitoring for toxic metals. Bioavailability of metals to plants depends on the pH of the soil, soil organic matter content, and the plant genotype. Plants can also accrue metals on their leaves in addition to metal uptake by their roots. It should also be realized that some toxic metals present in the environment will not absorb into the plant because they are strongly bound to soil colloids. Some of these metals include Cu, Co, Cr, and Pb. Of these metals, Cu, Co, and Pb are highly toxic to higher level plant species, as well as Hg, Ni, and Cd.1 It is our goal to determine which toxic metals can be found in the Chinese privet.
Research
Plan:
- Atomic Emission Theory: I will learn about atomic emission theory. I will also be trained to properly use the ICP-OES.
- Technique Preparation: I will develop techniques for preparing standards, prepare the standards, and practice how to use the instrument. I will also prepare calibration curves for various metals.
- Sample Collection: I will collect leaves and stems from Chinese privet plants that are harvested at specific controlled areas. I will begin the study of digestion procedures to make the samples homogenous liquids and analyze samples by ICP-OES.
- Additional Sample Collection: I will collect leaves and stems from Chinese privet plants that have colonized near industrial sites and compare them to control plot data.
Work on this project will commence during the summer of 2003 and continue into the 2003-2004 academic year, for which the PSRA funding is requested. I anticipate that I will discover exciting findings regarding toxic metals in the environment and I will present my results in a presentation form at a regional meeting of the American Chemical Society. This proposed research is extremely beneficial to my plans to attend graduate school in environmental chemistry or toxicology and to pursue a research-based career in environmental regulations for developing nations.
Conclusion
I propose to identify toxic metals present in the Tennessee River Valley by (1) collecting the Chinese privet (Ligustrum sinense), (2) using ICP-OES to analyze the environmental samples, and (3) making calibration curves with standard metals and (4) comparing with the unknown samples. The discovery of certain toxic elements in the Chinese privet can result in appropriate measures to limit the release of toxic metals in the environment.
Budget and Budget Justification
The solid samples collected for biomonitoring must be dissolved prior to analysis requiring digestion acids. The ICP-OES instrument requires a constant flow of argon gas. Standard solutions must be prepared in calibrated glassware. Therefore, I have allocated $500 for supplies and equipment including acids, argon and glassware. In addition, I plan to present the results of my research at a regional meeting of the American Chemical Society in the fall of 2003 and I propose $375.00 of the award for travel.